1. Field of the Invention
This invention relates to an automatic transmission equipped with planetary gear mechanism, brakes, clutches and one-way clutch, all housed within a casing (transmission casing), and adapted to change the transmission ratio by changing the torque transmission path of the planetary gear mechanism depending on operation states of the brakes, clutches and one-way clutch, and in particular to a mounting structure for the one-way clutch in such an automatic transmission.
2. Description of the Related Art
As is illustrated in FIG. 3, an automatic transmission TM has conventionally been provided on the output side of, for example, an automotive engine via a torque converter C which is equipped with a clutch CL. This automatic transmission TM is provided (not illustrated) with a shift-controlling hydraulic (fluid pressure) circuit.
Incidentally, this automatic transmission TM has a power train as shown in FIG. 3. Namely, FIG. 3 illustrates a casing (transmission casing) TMC, a front clutch C1, a rear clutch C2, an end clutch C3, a kick down brake B1, a low reverse brake B2, a one-way clutch OWC, a planetary gear mechanism PGM, a forward sun gear FS, a reverse sun gear RS, a short pinion gear SP, a long pinion gear LP, an annulus gear AG, a kick down drum KD and a carrier CA.
The gear shift pattern of the automatic transmission TM is summarized as follows.
______________________________________ Clutch Brake Shift position C1 C2 C3 OWC B1 B2 ______________________________________ P Neutral R Reverse X X N Neutral D First X X Second X X Third X X X OD (Fourth) X X ______________________________________
In the above table, letter "X" indicates that the respective clutch or brake is in engagement.
As is shown above, the automatic transmission TM changes the torque transmission path of the planetary gear mechanism PGM provided in the transmission casing TMC depending on operation states of the brakes B1,B2, clutches C1,C2,C3 and one-way clutch OWC also provided inside the transmission casing TMC, whereby the transmission ratio can be changed.
The mounting structure for the one-way clutch in the automatic transmission TM is depicted in FIG. 4. An inner race 1 of the one-way clutch OWC is provided on the side of the transmission casing TMC by way of a center support 2, while an outer race 3 is provided in such a way that the outer race 3 is fitted on an outer peripheral portion of the carrier CA of the planetary gear mechanism PGM.
In addition, the mounting of the outer race 3 to the carrier CA is effected by threaded engagement of plural bolts 4 in a wall portion of the carrier CA. Although not illustrated in FIG. 4, pins are provided between the bolts 4.
Plural sprags 5 are interposed between the inner race 1 and outer race 3 and further, ring-shaped end bearings 6,7 are also provided between the inner race 1 and outer race 3 so that these end bearings 6,7 are positioned along both ends of the sprags 5 respectively.
The low reverse brake B2 is also provided between a large-diameter outer peripheral portion of the outer race 3 and the transmission casing TMC.
Such a conventional mounting structure for a one-way clutch however requires high-accuracy concentricity between the inner race and the outer race so as to ensure the function of the one-way clutch. Accordingly, many components such as the transmission casing, center support, planetary gears and carriers are also required to have high-accuracy concentricity, thereby leading to a problem that a great deal of labor is required for their machining and assembly.
As the outer race is bolted on the carrier, there is another problem that the bolt securement must be strong enough to withstand the maximum torque faced by the one-way clutch.